Air Shift transmission

[wagon217]

Okay tossing this question out to see if anyone has some knowledge or experience with air shift transmissions. Know a fellow who has a 25 yr old Prevost rig with an air shift transmission. He cannot build enough air pressure on one tank to engage the transmission shift. The transmission is in Drive and of course the rig will not start in Drive. Any ideas how to work around this issue?

[jndwilli]

Have you tried hooking up an external compressor to the air tank on the bus and building up pressure that way?

[wagon217]

Yes ... but the problem is the external source can't build 140psi. So, still looking for a system that will produce that pressure.

[grndcontrol]

Trace Down the Nutral safety switch,it shoud be up by the air shifter transfer box disconnect this switch it should allow you to start the engine make shure you have you foot applied to the brake as the vehicle will immediatly to to move the old air shift system works off the same function as a standard transmission with an air servo working the shifting platform instead of manualy shifting like you would a semi truck the fack that you can't build up enough air pressure to apply air to the servo most like means that you have a majior leak or line obstruction or the compressior has failed if all else fails sometime rocking the unit back and forth gently while moving the shifter between nutral and drive will disengage the transmission or finding the supply tank and filling it externaly those trans are a real pain the A*** that's one reason you dont see a whole lot of them anymore they where the earliest form of automatic trans for there day